Switch for an on-load tap changer and load transfer switch for an on-load tap changer

ABSTRACT

An on-load tap-changer of a tap-changing transformer has a switch. The switch has: a take-off contact; a primary fixed contact; and a contact unit. The contact unit has a moving contact, a first arcing contact and a second arcing contact. These contacts are pivotable about a pivot axis during a switchover process such that the contacts assume a first position, in which they make contact with the take-off contact and the primary fixed contact, and a second position, in which they are separated from the take-off contact and the primary fixed contact. The second arcing contact assumes the first position before the first arcing contact when switching over from the second position to the first position and leaves the first position after the first arcing contact when switching over from the first position to the second position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2021/052053, filed on Jan.29, 2021, and claims benefit to German Patent Application No. DE 10 2020105 113.1, filed on Feb. 27, 2020. The International Application waspublished in German on Sep. 2, 2021 as WO 021/170340 A1 under PCTArticle 21(2).

FIELD

The present disclosure relates to a switch for an on-load tap-changer ofa tap-changing transformer and to a diverter switch for an on-loadtap-changer of a tap-changing transformer.

BACKGROUND

German patent application DE 10 2014 107 273 A1 discloses a switch for adiverter switch of an on-load tap-changer having a take-off contact, aprimary fixed contact and a plurality of primary moving contacts, whichare arranged in a stack in a contact carrier. In addition, the switchcomprises two structurally identical primary arcing contacts.

On-load tap-changers usually consist of a selector for power-freeselection of the respective winding tap of the transformer to which aswitchover is intended to be made, and a diverter switch for the actualload switchover from the previous winding tap to the new, selectedwinding tap. The switchover takes place by actuating different switches.This regularly produces arcs at the switching contacts, which melt orburn small amounts of the contact material and thus lead to contactwear. The wear is dependent on the current intensity and the duration ofthe arc at the respective contact. As the load increases, that is to sayat relatively high currents and voltages, the demands on the switchesand contacts are consequently also increased.

SUMMARY

In an embodiment, the present disclosure provides a switch for anon-load tap-changer of a tap-changing transformer. The switch has: atake-off contact; a primary fixed contact; and at least one contactunit. The contact unit has a plurality of contacts including a movingcontact, a first arcing contact and a second arcing contact. Theplurality of contacts are configured to be pivoted about a pivot axisduring a switchover process of the switch in such a way that theplurality contacts can each assume a first position, in which theplurality of contacts respectively make contact with the take-offcontact and the primary fixed contact, and a second position, in whichthe plurality of contacts respectively are separated from the take-offcontact and the primary fixed contact. The second arcing contact isconfigured to assume the first position before the first arcing contactwhen switching over from the second position to the first position andis configured to leave the first position after the first arcing contactwhen switching over from the first position to the second position.

BRIEF DESCRIPTION OF THE DRAWINGS

Subject matter of the present disclosure will be described in evengreater detail below based on the exemplary figures. All featuresdescribed and/or illustrated herein can be used alone or combined indifferent combinations. The features and advantages of variousembodiments will become apparent by reading the following detaileddescription with reference to the attached drawings, which illustratethe following:

FIG. 1 shows a perspective view of an advantageous embodiment of aswitch for an on-load tap-changer;

FIG. 2 shows a plan view of an advantageous embodiment of a diverterswitch for an on-load tap-changer, which comprises the switch of FIG. 1;

FIG. 3 shows a partial sectioned view of the switch from FIG. 1 ;

FIG. 4 shows a schematic illustration of an advantageous embodiment of adiverter switch; and

FIG. 5 shows a plan view of a further advantageous embodiment of thediverter switch.

DETAILED DESCRIPTION

Aspects of the present disclosure provide an improved switch for anon-load tap-changer and an improved diverter switch for a tap changerwhich withstands the increased loads at relatively high currents andvoltages.

According to a first aspect of the present disclosure, a switch for orin an on-load tap-changer of a tap-changing transformer is provided. Theswitch comprises a take-off contact, a primary fixed contact and atleast one contact unit. The contact unit has at least one movingcontact, a first arcing contact and a second arcing contact, whichcontacts can be jointly pivoted about a pivot axis during a switchoverprocess of the switch in such a way that they can each assume a firstposition, in which they make contact with the take-off contact and theprimary fixed contact, and a second position, in which they areseparated from the take-off contact and the primary fixed contact. Thesecond arcing contact assumes the first position before the first arcingcontact when switching over the contact unit from the second position tothe first position and the second arcing contact leaves the firstposition after the first arcing contact when switching over from thefirst position to the second position.

The temporally successive processes of the first and the second arcingcontact assuming and leaving the first position causes the current to beswitched off to be, as it were, “transferred” from one arcing contact tothe other. In technical terms, this process is also called“commutation”. In more general terms, “commutation” is thereforeunderstood to mean the transfer of a current from one current branch toanother current branch, with both branches carrying current during thecommutation time.

According to at least one embodiment, the first arcing contact assumesthe first position before the at least one moving contact when switchingover the contact unit from the second position to the first position andthe first arcing contact leaves the first position after the at leastone moving contact when switching over from the first position to thesecond position.

In this way, a further commutation stage is created and the duration ofthe arc and the contact wear on the moving contact and the arcingcontacts are further reduced.

This multi-stage commutation has the advantage that the duration of anarc at the first and the second arcing contact or the moving contact isshortened, and therefore the contact wear at the first and the secondarcing contact or the moving contact is also reduced.

According to at least one embodiment, the moving contact, the firstarcing contact and the second arcing contact consist of differentconductive materials which have a different conductivity.

The moving contact preferably consists of copper, the first arcingcontact preferably consists of brass and the second arcing contactpreferably consists of stainless steel.

The contact wear can be influenced by the choice of material due to theproperties of the material. In particular, it is important for thecontacts to wear uniformly, so that the staggering of the contact-makingand lifting-off points over time and the sequence of contact-making andlifting-off operations of the moving contact, the first arcing contactand the second arcing contact are maintained. This is because otherwisethere may be faults and malfunctions on the switch and consequently onthe entire on-load tap-changer.

According to at least one embodiment, the moving contact and/or thefirst arcing contact and/or the second arcing contact have a differentgeometric shape.

In particular, the cross section of the respective contact through whichthe current flows can be reduced by providing cutouts in an arcingcontact and/or a moving contact. This has the advantage that theelectrical conductivity of the arcing contacts and/or of the movingcontact can optionally be further adjusted by means of the geometricshape of the contacts in order to achieve uniform wear.

According to at least one further embodiment, the at least one movingcontact, the first arcing contact and the second arcing contact eachhave two contact regions by way of which they rest against the take-offcontact and the associated fixed contact in the first position.

At least one of the two contact regions can consist of a material thatdiffers from the material of the rest of the contact, for example of anarc-resistant copper-tungsten sintered material.

According to at least one embodiment, the first arcing contact and thesecond arcing contact are arranged relative to the moving contact insuch a way that at least one contact region of the first arcing contactand/or of the second arcing contact protrudes in relation to the contactregions of the moving contact in the second position.

According to at least one embodiment, the second arcing contact isarranged relative to the first arcing contact in such a way that atleast one contact region of the second arcing contact protrudes inrelation to the contact regions of the first arcing contact in thesecond position.

A contact region that protrudes in relation to the other contact regionscauses the corresponding contact to meet the take-off contact and/or theprimary fixed contact earlier than the contacts that have no contactregion or a less protruding contact region when switching over to thefirst position and also again leaves the take-off contact and/or theprimary fixed contact later in the return movement when switching overfrom the first position to the second position. As a result, theduration of an arc on a contact and the contact wear can be influenced.

According to at least one embodiment, the switch comprises a contactcarrier which is mounted pivotably about the pivot axis and has a firstsupporting plate and a second supporting plate which is arrangedparallel to the first supporting plate. Furthermore, the contact carriercomprises at least one further moving contact, wherein the movingcontacts, the first arcing contact and the second arcing contact arearranged between the supporting plates. The moving contacts arepreferably identical to one another in shape and material.

According to at least one embodiment, the moving contacts and the firstarcing contact and the second arcing contact are arranged in a stack inthe contact carrier. For fastening in the contact carrier, the movingcontacts, the first arcing contact and the second arcing contact eachhave two parallel elongate holes situated one above the other. They arefitted movably between the supporting plates by means of guide pinswhich pass through the elongate holes.

The moving contacts, the first arcing contact and the second arcingcontact can be arranged in a stack spaced apart from one another bydisks which lie between the individual contacts and are pushed onto theguide pins.

According to at least one embodiment, the guide pins together with theelongate holes, during the switchover process of the switch, form amechanical stop for the moving contacts and the first and the secondarcing contact in relation to the force exerted by compression springswhich are arranged on the back surfaces, facing away from the contactregions, of the contacts.

According to at least one embodiment, the elongate holes of the movingcontacts, of the first arcing contact and of the second arcing contactare each of different lengths in such a way that the moving contacts,the first arcing contact and the second arcing contact each reach themechanical stop at different points in time during the switchoverprocess of the switch or of the contact unit from the second to thefirst position and/or from the first to the second position. Provisioncan be made for the elongate holes of the first arcing contact to beshorter than the elongate holes of the second arcing contact and longerthan the elongate holes of the moving contacts.

In the second position, the moving contacts and the first and the secondarcing contacts each rest against the guide pins by way of the ends,facing away from the contact regions, of the elongate holes. This cancause the second arcing contact to protrude further beyond the guidepins than the first arcing contact, and this in turn protrudes furtherthan the moving contacts. As a result, the moving contacts, the firstarcing contact and the second arcing contact reach the take-off contactand the primary fixed contact one after the other during the switchoverprocess of the switch or the contact unit from the second to the firstposition and also leave the take-off contact and the primary fixedcontact again one after the other when switching over from the firstposition to the second position.

According to at least one embodiment, the moving contacts, the firstarcing contact and the second arcing contact are arranged on the contactcarrier in such a way that they are preloaded in a resilient manneragainst the take-off contact and the primary fixed contact in the firstposition.

According to at least one embodiment, the moving contacts, the firstarcing contact and the second arcing contact are arranged in a stack insuch a way that the moving contacts are arranged between the firstarcing contact and the second arcing contact. In principle, however, anypossible arrangement of the contacts in a stack is possible.

According to at least one embodiment, the switch comprises a secondaryfixed contact and a second contact unit which, with respect to an axisof symmetry which runs through the pivot axis, is arranged symmetricallyto the contact unit.

The second contact unit is constructed analogously to the first contactunit and accordingly has a third arcing contact, which is identical tothe first arcing contact, and a fourth arcing contact, which isidentical to the second arcing contact. The fourth arcing contact lieson a plane with the first arcing contact and the third arcing contactlies on a plane with the second arcing contact.

According to at least one embodiment, the switch is in the form of apermanent main switch or in the form of a disconnecting switch for or ina diverter switch of an on-load tap-changer.

According to a second aspect of the present disclosure, the objectmentioned at the outset is achieved by a diverter switch for or in anon-load tap-changer of a tap-changing transformer. The diverter switchhas a switch designed according to the first aspect of the presentdisclosure with at least one contact unit. In addition, the diverterswitch has a first current path which comprises the moving contact ofthe contact unit of the switch, a second current path which comprisesthe first arcing contact of the switch, a third current path whichcomprises the second arcing contact of the switch, a fourth current pathwhich comprises at least one vacuum interrupter and a fifth current pathwhich connects the switch to a take-off lead.

The first current path has a particular resistance which results fromthe specific resistance of the material from which the moving contactsare composed. The second current path has a resistance which is greaterthan the resistance of the first current path and the third current pathhas a resistance which is greater than the resistance of the secondcurrent path. By designing the resistances of the current paths usingthe designated procedure, low and largely uniform wear of the contactsof the switch is made possible with multi-stage commutation of the loadcurrent.

According to a preferred embodiment, the resistances of the second andof the third current path can be determined using the material of therespective arcing contact or the specific resistance of the materialfrom which the respective arcing contact, which is a constituent part ofthe path, is composed and/or using the geometric shape of said arcingcontact.

The resistance of the fourth current path results, in some cases, fromthe material of the contacts or the specific resistance of the materialof the contacts of the at least one vacuum interrupter, the fourthcurrent path comprising said vacuum interrupter.

The resistance of the fifth current path results from the material ofthe line or the specific resistance of the material from which the linethat connects the switch to the take-off lead is composed.

According to a preferred embodiment, the diverter switch has a switchwith a second contact unit, wherein the diverter switch has at leastthree further current paths which comprise the moving contacts of thesecond contact unit and a third arcing contact and a fourth arcingcontact of the second contact unit and which are designed analogously tothe first, the second and the third current path.

According to a further preferred embodiment, the diverter switch has aswitch with a second contact unit, wherein the diverter switch has fivefurther current paths which are designed analogously to the first, thesecond, the third, the fourth and the fifth current path.

Further features, advantages and possible applications of the presentdisclosure can be found in the following description of the exemplaryembodiments and in the figures. Here, all features described and/orillustrated in the figures form the subject matter of the presentdisclosure alone and in any desired combination even irrespective oftheir composition in the individual claims or their dependencyreferences.

Components which are identical or functionally identical or which havean identical effect may be provided with identical reference signs.Identical components or components with an identical function are insome cases explained only in relation to the figure in which they firstappear. The explanation is not necessarily repeated in the subsequentfigures.

FIG. 1 shows a perspective view of an advantageous embodiment of aswitch 10 for an on-load tap-changer 40.

In this embodiment, the switch 10 comprises a take-off contact 13, aprimary fixed contact 14 and a secondary fixed contact 15. Furthermore,the switch 10 has a first contact unit 12, which is in a first positionin which it makes contact with the take-off contact 13 and the primaryfixed contact 14, and a second contact unit 37, which is in a secondposition in which it is separated from the take-off contact 13 and thesecondary fixed contact 15. The contact units 12, 37 are arranged in acontact carrier 20 and mounted pivotably relative to the take-offcontact 13 and the fixed contacts 14, 15 about a pivot axis 21 in such away that they can each assume the first position and the secondposition. The first contact unit 12 comprises a contact stack with afirst arcing contact 17, a second arcing contact 18 and a plurality ofmoving contacts 16 arranged between the arcing contacts 17 and 18. Thesecond contact unit 37 likewise comprises a contact stack with a thirdarcing contact 38, a fourth arcing contact 39 and a plurality of movingcontacts 16 situated between the arcing contacts 38 and 39. The take-offcontact 13, the fixed contacts 14, 15 and the moving contacts 16, whichare structurally identically to one another, consist of copper. Thefirst and the third arcing contact 17, 38 are structurally identicallyto one another and consist of brass. The second and the fourth arcingcontact 18, 39 are likewise structurally identical to one another andconsist of stainless steel.

The contact carrier 20 has a first supporting plate 201 and a secondsupporting plate 202, between which the contact stacks of the twocontact units 12 and 37 are arranged. The supporting plates 201, 202 arestructurally identical, arranged parallel and in alignment one above theother and consist of metal. The arcing contacts 17, 18, 38, 39 each havecontact regions 23 by way of which they rest on the take-off contact 13and one of the fixed contacts 14 and 15 in the first position. Based onthe second contact unit 37, which is in the second position, it can beseen that the contact regions 23 on the outside with respect to thepivot axis 21 are at a greater distance from the fixed contacts 14 or 15than the contact regions 23 on the inside are from the take-off contact13.

FIG. 2 shows a plan view of an advantageous embodiment of a diverterswitch 30 for an on-load tap-changer 40, which comprises the switch 10from FIG. 1 . Here, the contact unit 37 is in the first position and thecontact unit 12 is in the second position. The supporting plate 201 ishidden in FIG. 2 , so that the internal structure of the contact carrier20 can be seen. The two contact units 12 and 37 are arrangedsymmetrically to one another with respect to an axis of symmetry 22 inthe contact carrier 20.

In this embodiment, the on-load tap-changer 40 comprises the diverterswitch 30, a switching shaft 41 for driving the switch 10, and a contactcylinder 44 through which the switching shaft 41 runs coaxially. Thetake-off contact 13 and the fixed contacts 14, 15 are routed through thecontact cylinder 44 and fastened to it. The contact carrier 20 comprisesa lever 50 with arms 501, 502, 503 arranged in a Y-shape and a fork 51.The lever 50 is arranged between the supporting plates 201, 202 andfastened to them by way of a plurality of pins which pass through thefree ends of the side arms 501, 502 and a central portion of the centralarm 503. The fork 51 is fixed to the lever 50 between the two side arms501, 502 on the side averted from the central arm 503 and has anelongate hole which runs in extension of the central arm 503 and is openat its outer end remote from the lever 50. The contact stacks 16/17/18and 16/38/39 are fitted movably to the supporting plates 201, 202 by wayof in each case two guide pins 32 which pass through parallel elongateholes 31 in the contact stacks 16/17/18, 16/38/39 and consist of metal.The free end of the central arm 503 is mounted pivotably about the pivotaxis 21. Therefore, the supporting plates 201, 202 and consequently alsothe contact carrier 20, the fork 51 and the contact stacks 16/17/18,16/38/39 are mounted pivotably about the pivot axis 21 relative to thetake-off contact 13 and the fixed contacts 14, 15. The contact stacks16/17/18, 16/38/39 and the contact carrier 20 therefore form a one-sidedlever in relation to the pivot axis 21.

The contact stacks 16/17/18, 16/38/39 are arranged symmetrically to thelever 50 on both sides of the central arm 503 and are supported by wayof their back surfaces, facing away from the contact regions 23, viacompression springs (FIG. 3 ) on the side arms 501, 502. As a result,the contact stacks 16/17/18, 16/38/39 are fitted to the contact carrier20 in such a way that they are they are each preloaded in a resilientmanner against the take-off contact 13 and the associated fixed contact14, 15 in their first position.

The guide pins 32 together with the elongate holes 31 form a mechanicalstop for the moving contacts 16 and the first, the second, the third andthe fourth arcing contact 17, 18, 38, 39 against the force exerted onthem by the compression springs (FIG. 3 ) during the switchover processof the switch 10, that is to say during the pivoting movement of thecontact stacks 16/17/18, 16/38/39. Here, the elongate holes 31 of themoving contacts 16, those of the first and of the third arcing contact17, 38 and those of the second and of the fourth arcing contact 18, 39are each of different lengths. The elongate holes of the second and ofthe fourth arcing contact 18, 39 are the longest. Specifically, thismeans that the second arcing contact 18 reaches the take-off contact 13and the primary fixed contact 14 as the last contact of the contactstack 16/17/18 during a switchover process of the first contact stack16/17/18 from the second to the first position and also leaves themagain as the last contact of the contact stack 16/17/18 during aswitchover process from the first position to the second position. Theelongate holes of the first and of the third arcing contact 17, 38 areshorter than the elongate holes of the second and of the fourth arcingcontact 18, 39 and longer than the elongate holes of the moving contacts16. Specifically, this means that the first arcing contact 17 reachesthe take-off contact 13 and the primary fixed contact 14 after thesecond arcing contact 18 and before the moving contacts 16 during aswitchover process of the first contact stack 16/17/18 from the secondto the first position and leaves them again after the moving contacts 16but before the second arcing contact 18.

The diverter switch 30 further comprises a base plate 45 of a frame, atriangular driver 42 and a drive roller 43. The switching shaft 41 andthe lever 50 are mounted rotatably on the base plate 45. The driver 42is seated non-rotatably on the switching shaft 41 and supports the driveroller 43 in one corner. The drive roller 43 is seated displaceably inthe elongate hole of the fork 51, so that a rotation of the switchingshaft 41, via the driver 42, the drive roller 43 and the fork 51, pivotsthe lever 50 in the opposite direction about the pivot axis 21 and thispivoting movement is transferred to the contact stacks 16/17/18,16/38/39 via the plurality of pins, the supporting plates 201, 202 andthe four guide pins 32.

In FIG. 2 , the diverter switch 30 is in a stationary position, in whichthe drive roller 43 is seated at the outer end of the elongate hole inthe fork 51. The drive roller 43 presses the contact stack 16/38/39against the take-off contact 13 and the fixed contact 15 via the twoguide pins 32 associated with it. The mechanical stop, formed by theelongate holes 31 and the guide pins 32, for the moving contacts 16 andthe arcing contacts 38 and 39 on the side facing the take-off contact 13and the fixed contact 15 is reached. The contact stack 16/17/18separated from the take-off contact 13 and the fixed contact 14 ispressed against the two guide pins 32 associated with it by thecompression springs associated with it (FIG. 3 ). Therefore, the movingcontacts 16 are electrically conductively connected to one another andto the arcing contacts 17, 18. The same applies analogously when thecontact stack 16/38/39 is separated from the take-off contact 13 and thefixed contact 15.

The contact stacks 16/17/18, 16/38/39 are arranged symmetrically to thelever 50 on both sides of the central arm 503 in such a way that thefourth arcing contact 39 lies on a plane with the first arcing contact17 and the third arcing contact 38 lies on a plane with the secondarcing contact 18. The second and fourth arcing contacts 18, 39 have aplurality of cutouts 52 in the stainless steel contact carrier, similarto a honeycomb structure, which increases the resistance of the arcingcontacts or reduces the electrical conductivity.

FIG. 3 shows a partial sectioned view of the switch 10 from FIGS. 1 and2 , in particular the contact stack 16/17/18 of the contact unit 12 inthe region situated on the outside with respect to the pivot axis 21.Said figure shows the contact stack 16/17/18 in the second position onthe left and in the first position on the right. The compression springs46 are arranged between the back surfaces of the first arcing contact17, of the second arcing contact 18 and of the moving contacts 16 andthe side arm 501. On the left-hand side, the guide pin 32 rests againstthe elongate holes 31 of the contacts on the side averted from the fixedcontact 14 and, on the right-hand side, the guide pin 32 rests againstthe elongate holes 31 of the contacts on the side facing the fixedcontact 14. It can be seen on both sides that the elongate hole 31 ofthe second arcing contact 18 is the longest and the elongate hole 31 ofthe first arcing contact 17 is shorter than that of the first arcingcontact 18, but longer than the elongate hole of the moving contacts 16.

In the second position, shown on the left-hand side, the compressionsprings 46 press the contact stack 16/17/18 against the guide pin 32. Onaccount of the different lengths of the elongate holes 31, the contactregion 23 of the second arcing contact protrudes in relation to thecontact regions 23 of the first arcing contact 17 and of the movingcontacts 16. The contact region 23 of the first arcing contact 17projects in relation to the contact regions 23 of the moving contacts16.

The contact stack 16/38/39 is constructed analogously, except for thefirst and the second arcing contact 38 and 39 which are arranged in amanner swapped in relation to the contact stack 16/17/18.

FIG. 4 shows a schematic illustration of an advantageous embodiment of adiverter switch 30. The diverter switch 30 has a switch 10 with at leastone contact unit 12, which can be designed according to FIGS. 1 to 3 ,and five current paths, the number of current paths in the diverterswitch 30 not being limited to five. A first current path 61 whichcomprises the moving contacts 16 of the contact unit 12 and has a firstresistance R1 and a first impedance L1, a second current path 62 whichcomprises the first arcing contact 17 of the contact unit 12 and has asecond resistance R2 and a second impedance L2, a third current path 63which comprises the second arcing contact 18 of the contact unit 12 andhas a third resistance R3 and a third impedance L3, a fourth currentpath 64 which comprises a vacuum interrupter 19 and has a fourthresistance R4 and a fourth impedance L4, and a fifth current path 65which connects the switch 10 to a take-off lead 60 and has a fifthresistance R5 and a fifth impedance L5.

FIG. 5 shows a plan view of a further advantageous embodiment of thediverter switch 30. This embodiment is similar to the embodiments thathave been described with reference to FIGS. 1 and 2 , and thereforeprimarily the differences will be explained in more detail below.

In this embodiment, the diverter switch 30 has three sectors, each witha switch 10. With regard to the switches 10, reference is made to theprevious explanations in an analogous manner. A drive roller 43 isarranged in each of the corners of the driver 42. The three driverollers 43 and the three switches 10 are arranged offset through 120°around the switching shaft 41 and are actuated synchronously by rotatingthe switching shaft 41.

It is assumed that the present disclosure and many of the attendantadvantages thereof can be understood from the above description.Furthermore, it is clear that various changes can be made to the shape,construction and arrangement of the components without departing fromthe disclosed subject matter or without sacrificing all materialadvantages. The embodiment described is merely explanatory and suchchanges are intended to be covered by the following claims. Furthermore,it is understood that the invention is defined by the following claims.

While subject matter of the present disclosure has been illustrated anddescribed in detail in the drawings and foregoing description, suchillustration and description are to be considered illustrative orexemplary and not restrictive. Any statement made herein characterizingthe invention is also to be considered illustrative or exemplary and notrestrictive as the invention is defined by the claims. It will beunderstood that changes and modifications may be made, by those ofordinary skill in the art, within the scope of the following claims,which may include any combination of features from different embodimentsdescribed above.

The terms used in the claims should be construed to have the broadestreasonable interpretation consistent with the foregoing description. Forexample, the use of the article “a” or “the” in introducing an elementshould not be interpreted as being exclusive of a plurality of elements.Likewise, the recitation of “or” should be interpreted as beinginclusive, such that the recitation of “A or B” is not exclusive of “Aand B,” unless it is clear from the context or the foregoing descriptionthat only one of A and B is intended. Further, the recitation of “atleast one of A, B and C” should be interpreted as one or more of a groupof elements consisting of A, B and C, and should not be interpreted asrequiring at least one of each of the listed elements A, B and C,regardless of whether A, B and C are related as categories or otherwise.Moreover, the recitation of “A, B and/or C” or “at least one of A, B orC” should be interpreted as including any singular entity from thelisted elements, e.g., A, any subset from the listed elements, e.g., Aand B, or the entire list of elements A, B and C.

REFERENCE SIGNS

10 Switch

12 Contact unit

13 Take-off contact

14 Primary fixed contact

15 Secondary fixed contact

16 Moving contacts

17 First arcing contact

18 Second arcing contact

19 Vacuum interrupter

20 Contact carrier

201 First supporting plate

202 Second supporting plate

21 Pivot axis

22 Axis of symmetry

23 Contact regions

30 Diverter switch

31 Elongate holes

32 Guide pin

37 Second contact unit

38 Third arcing contact

39 Fourth arcing contact

40 On-load tap-changer

41 Switching shaft

42 Driver

43 Drive roller

44 Contact cylinder

45 Base plate

46 Compression springs

50 Lever

501/502/503 Arms of lever 50

51 Fork

52 Cutouts

60 Take-off lead

61 First current path

62 Second current path

63 Third current path

64 Fourth current path

65 Fifth current path

R1, R2, R3, R4, R5 Resistances of 61 to 65

L1, L2, L3, L4, L5 Impedances of 61 to 65

1. A switch for an on-load tap-changer of a tap-changing transformer,the switch comprising: a take-off contact; a primary fixed contact; atleast one contact unit comprising a plurality of contacts comprising amoving contact, a first arcing contact and a second arcing contact, theplurality of contacts being configured to be pivoted about a pivot axisduring a switchover process of the switch in such a way that theplurality contacts can each assume a first position, in which theplurality of contacts respectively make contact with the take-offcontact and the primary fixed contact, and a second position, in whichthe plurality of contacts respectively are separated from the take-offcontact and the primary fixed contact; wherein the second arcing contactis configured to assume the first position before the first arcingcontact when switching over from the second position to the firstposition and is configured to leave the first position after the firstarcing contact when switching over from the first position to the secondposition.
 2. The switch as claimed in claim 1, wherein the first arcingcontact is configured to assume the first position before the movingcontact when switching over from the second position to the firstposition and is configured to leave the first position after the movingcontact when switching over from the first position to the secondposition.
 3. The switch as claimed in claim 1, wherein the movingcontact, the first arcing contact and the second arcing contact consistof different materials which have a different electrical conductivity.4. The switch-(-4-0) as claimed in claim 1, wherein the moving contact,and/or the first arcing contact, or the second arcing contact have adifferent geometric shape.
 5. The switch as claimed in claim 1, whereinthe moving contact, the first arcing contact, and the second arcingcontact each have contact regions by way of which the plurality ofcontacts respectively rest against the take-off contact and the fixedcontact in the first position.
 6. The switch as claimed in claim 1,wherein the first arcing contact and the second arcing contact arearranged relative to the moving contact in such a way that at least onecontact region of the first arcing contact or of the second arcingcontact protrudes in relation to the contact regions of the movingcontact in the second position.
 7. The switch as claimed in claim 1,comprising: a contact carrier comprising a first supporting plate and asecond supporting plate that is arranged parallel to the firstsupporting plate; and at least one further moving contact, wherein: themoving contact, the further moving contact, the first arcing contact,and the second arcing contact are fitted to the supporting plates andare arranged between the supporting plates.
 8. The switch as claimed inclaim 1, wherein: the moving contact, the first arcing contact and thesecond arcing contact are arranged in a stack in the contact carrier andeach have parallel elongate holes situated one above the other; themoving contact, the first arcing contact and the second arcing contactare fitted movably between the supporting plates by guide pins whichpass through the elongate holes.
 9. The switch as claimed in claim 1,wherein the guide pins together with the elongate holes form amechanical stop for the moving contact, the first arcing contact and thesecond arcing contact during the switchover process of the switch. 10.The switch as claimed in claim 1, wherein the elongate holes of themoving contact, of the first arcing contact, and of the second arcingcontact are each of different lengths in such a way that the movingcontact, the first arcing contact and the second arcing contact reachthe mechanical stop at different points in time during the switchoverprocess of the switch.
 11. The switch as claimed in claim 1, wherein themoving contact, the first arcing contact, and the second arcing contactare arranged on the contact carrier in such a way that the plurality ofcontacts are preloaded in a resilient manner against the take-offcontact and the primary fixed contact in the first position.
 12. Theswitch as claimed in claim 1, wherein the moving contact, the firstarcing contact, and the second arcing contact are arranged in a stack insuch a way that the moving contact is arranged between the first arcingcontact and the second arcing contact.
 13. The switch as claimed inclaim 1, comprising a secondary fixed contact and a second contact unitwhich, with respect to an axis of symmetry which runs through the pivotaxis, is arranged symmetrically to the contact unit and has comprises athird arcing contact, which is identical to the first arcing contact,and a fourth arcing contact, which is identical to the second arcingcontact, wherein the fourth arcing contact lies on a plane with thefirst arcing contact and the third arcing contact lies on a plane withthe second arcing contact.
 14. The switch as claimed in claim 1, in theform of a permanent main switch or in the form of a disconnecting switchfor or in a diverter switch of an on-load tap-changer.
 15. A diverterswitch for or in an on-load tap-changer of a tap-changing transformer,the diverter switch comprising: the switch as claimed in claim 1: afirst current path-K-14 which comprises the moving contact of theswitch; a second current path which comprises the first arcing contactof the switch; a third current path which comprises the second arcingcontact of the switch; a fourth current path which comprises at leastone vacuum interrupter; a fifth current path which connects the switchto a take-off lead, wherein: the first current path has a resistance,the second current path has a resistance which is greater than theresistance of the first current path, the third current path has aresistance which is greater than the resistance of the second currentpath.
 16. The diverter switch as claimed in claim 1, wherein theresistances of the second current path and the resistance of the thirdcurrent path are determined using a material of the respective arcingcontact or using the geometric shape of the respective arcing contact.